If your Wii is Korean and has been modified to USA formware then your Wii is now bricked. No cure as far as I am aware. 4.2 kills Korean modified Wiis, and you are right, you should have searched first.

1 User Says Thank You Tealc For This Useful Post

OK,Thanks Bro,Is There Any Way I Can Enter Wii Menu Like A Safe Mode Same As Windows?...Then I Could Reboot It To My Previous Ver. ?........
And Would It Help If I Went To The Shop I Bought It From And Ask Then To Re-Hack It Back?

I really don't know about the returning it thing. Nintendo are refusing to repair 003 Wiis so whether your shop will take it from you is up to them.

Recovery menu exists on 003 Wiis but I don't think anyone has been able to do anything from there because 4.2 update took away boot2, IOS249, IOS222, IOS223 etc and leaves you in a very trickyt situation. Search for the term savemiifrii.

There's a very long thread in the Bricked section about 003 Wiis, maybe that'll help you.

I really don't know about the returning it thing. Nintendo are refusing to repair 003 Wiis so whether your shop will take it from you is up to them.

Recovery menu exists on 003 Wiis but I don't think anyone has been able to do anything from there because 4.2 update took away boot2, IOS249, IOS222, IOS223 etc and leaves you in a very trickyt situation. Search for the term savemiifrii.

There's a very long thread in the Bricked section about 003 Wiis, maybe that'll help you.

Yes I have Read The Long Post,And Thank You For Your Help,Its Been A Pleasure Working With You,And Now I Would Like To Cry,I Have Just Wasted $400 SGD.......